The synthesis of germanium nanomaterials with well-defined surface chemistry is of considerable interest because of not only general scientific curiosity but also their vast potential in optoelectronics, energy storage, and the semiconductor industry. Herein, we report a straightforward preparative route that yields hydride-terminated germanium nanosheet (H-GeNS) monolayers via sonochemical exfoliation of hydride-terminated germanane flakes (HGe-flakes) derived from crystalline CaGe2. We subsequently show that these freestanding H-GeNSs are readily functionalized by radical-initiated and thermally induced hydrogermylation. Furthermore, we demonstrate that following functionalization the crystal structure of the GeNSs remains intact, and the introduction of organic moieties to the GeNS surfaces imparts improved thermal stability and solvent compatibility.